Influence of current density on microstructure and dielectric properties during the flash sintering of strontium titanate ceramics

Flash sintering (FS), as a novel sintering technique, has enormous potential in taking powder particles into dense ceramics. Here, dense SrTiO3 ceramics with small grain size and excellent electrical properties (ε = 453, tan δ = 0.002) can be flash sintered at furnace temperature of 1145 ℃ via combining a field of 150 V/cm and a current density of 40 mA/mm2. The effect of current density limits on the microstructure morphology, density, phase structure and dielectric properties of SrTiO3 ceramics is investigated. It is shown that the current density parameter is of great importance in the control of the densification behavior and grain growth during flash sintering: the grain size increases gradually with raising the current density, while the density increases first and then slightly decreases. Moreover, the onset temperature of flash sintering and phase structure is independent of the current density in this experiment. These ceramics exhibit a satisfactory correspondence between electrical properties and structure. Based on the black-body radiation analysis, the ability of Joule heating to cause flash sintering is limited. Thus, the avalanche multiplication model was combined to help understand the origin of flash sintering.